Data communication systems having a microprocessor structure, with a tightly coupled multiprocessing (TCMP) system having a system configuration in which a plurality of microprocessors share a single memory device have been widely used. However, the loosely coupled multiprocessing system in which each processor has its own memory device is more popularly used in order to improve the system performance when increasing the number of processor modules.
In a loosely coupled multiprocessing system, general purpose buffers, having the same construction, are used for the buffers on the transmitting side and the receiving side as message storage regions, and the message transfer is made between these general purpose buffers.
However, when making message communication using such general purpose buffers, the message which is the subject of the communication cannot be stored in the general purpose buffer if the size of this message is large, and for this reason, it is necessary to communicate the message in divisions.
When executing the message communication according to this method, the message which is the subject of the transmission must, at the transmitting side processing module, be expanded to the general purpose buffer from the original memory position. In addition, at the receiving side processing module, it is necessary to expand the message which is received at the general purpose buffer to the requested memory position. For this reason, it takes too much time for the message transmission and reception process if the size of the message is large.
Therefore, a conventional message control system for the loosely coupled multiprocessing system has a problem in that it is impossible to promptly execute data processing which requires large messages to be transmitted and received.
The present invention takes the above noted problems into consideration, and has as an object to provide a message control system for a data communication system employing loosely coupled processing modules, which eliminates the above noted problems by making it possible to execute message communication without requiring the structures of the transmitting and receiving buffers to match.